Alignment issue?

[matt heinzel]

Our engraver just brought me some tags and when I looked at them there was something wrong with them. On one the left edge you can see that it cut, but then just to the right you can see another small "shadow cut". Then on the right side of the tag it looks like a step where the beginning of the cut starts and ends. Is this an alignment issue or maybe something else. I have also noticed that some times there is a burn where it starts and stops on cut job.

Universal laser PLS 360 being used.

[Scott Shepherd]

Matt, that can come from the material physically moving while cutting, which I have seen many, many times, or it could be the belts/bearings/pulleys need to be replaced. On our PLS, when we start seeing that, we do the $500 kit of whatever it is that it all new belts, bearings, and pulleys. It seems to fix it for us. How many hours do you have on the machine that's doing that? Have you changed any of those items recently? Or ever?

[matt heinzel]

I haven't replaced the belt and bearings in a while. We have them in stock so I guess that will be a first step. The material was cut from a full sheet so I'm guessing it didn't move.

[Kev Williams]

I've never changed a bearing. 2 belts on the ULS and 1 on the LS900, in 13 and 11 years. The ULS needs a new belt, the main wear area (the first 3" of travel) is pretty worn, the engraving shows a bit of shadow or wobble in that area. I've had a new belt to put on for several years, just haven't changed it. For awhile now I've been offsetting my X and Y by 4" and 2". No issues. If I have a big enough part that requires those inches, I just slow the machine down, works fine...

I say all this because I've never noticed more than about .005" runout due to a worn belt, and like I said, I've never changed a bearing. The offset in his pics is closer to .020"...

If I read the pics right, the offset it at the top (or bottom?) corners only, none at the bottom. This could be due to material moving or warping as its cut, but those 2 corners only indicates twist. If that edge of the plate was warping badly towards the lens head, that could be it. The other cause of 'twist' might be one of the Y axis rails, or drive rods may be loose. If one side of the X rail moves different than the other side, this type of offset can be the result...

Both my ULS and LS900 had this happen several years ago, in both machines one of the drive rod set screws was loose. The misalignment doesn't show up much when rastering because the rail only moves one direction...

[Scott Shepherd]

The test we run is to make a circle, about 3/4" or 1", and then vector mark the circle. If the ends match, the material is moving in your example. It doesn't matter it's a full sheet, it'll move within the kerf. Seen it many times. If the ends don't match, then it's the belts/bearings, etc.

We've always used the kit, so it's easy to do the belts, bearings, pulleys all at once. In every case, it's made the start and finish of the circle line up perfectly after it's all be replaced.